Does climate vary more from century to century when it is warmer?
Century-scale climate variability was enhanced when the Earth was warmer during the Last Interglacial period (129-116 thousand years ago) compared to the current interglacial (the last 11,700 years), according to a new UCL-led study.
The findings, published today in Nature Communications and funded by the Natural Environment Research Council (NERC) and the Australian Research Council (ARC), reveal that the Last Interglacial period was punctuated by a series of century-scale arid events in southern Europe and cold water-mass expansions in the North Atlantic.
Assessing natural climate variability under relatively warm conditions is crucial to inform projections under future carbon emission scenarios. Professor Chronis Tzedakis (UCL Geography), study lead author, said: “The Last Interglacial is particularly relevant because it provides insights into climate processes during a period of excess warmth.”
The Last Interglacial period contained an interval of intense Arctic warming, with surface air temperatures estimated at 3-11°C above pre-industrial, comparable to high-latitude warming scenarios for the end of this century.
Global sea-level during the Last Interglacial is estimated to have been ~6-9 m above present, with 0.6-3.5 m derived from melting of the Greenland Ice Sheet.
Previously, several North Atlantic and European records have detected century-scale changes in temperature and precipitation within the Last Interglacial, but there has been considerable uncertainty over the timing, extent and origin of these climate oscillations.
This new study by international researchers from twelve institutions used marine and terrestrial geological archives, coupled with climate model experiments, to create the most detailed timeline of ocean and atmosphere changes in the North Atlantic and southern Europe during the Last Interglacial.
To address the uncertainties in comparing records from different environments, researchers produced a “stratigraphic ‘rosetta stone’ by analysing different fossils from the same sediment samples in a marine core off Lisbon,” said Dr Luke Skinner (Cambridge University) who led the palaeoceanographic analyses.
“The marine core also contained pollen transported from the Tagus river into the deep sea, thus enabling a direct comparison of vegetation and North Atlantic ocean changes,” said Dr Vasiliki Margari (UCL Geography), who undertook the pollen analysis.
Changes in vegetation, primarily caused by variations in the amount of rainfall, were then linked to changes in the chemical signature of rainfall recorded in stalagmites from Corchia Cave in northern Italy.
“The Corchia record is particularly important because it is supported by very detailed radiometric dating using the decay of uranium isotopes, producing one of the best chronologies for this period available,” said Dr Russell Drysdale (University of Melbourne), who led the team studying the Italian cave.
Climate model experiments, undertaken by Dr Laurie Menviel and Dr Andrea Taschetto of the University of New South Wales Sydney, revealed that the spatial fingerprint of these changes was consistent with disruptions of the Atlantic meridional overturning circulation.
Greenland ice-melt and runoff as a result of strong high-latitude warming during the Last Interglacial may have contributed to the weakening of the Atlantic meridional overturning circulation and to the observed climate changes.
“Although not a strict analogue for future anthropogenically-driven changes, the profile of the Last Interglacial that emerges is one of enhanced century-scale climate instability, with implications for ice-sheet and ocean dynamics,” said Professor Tzedakis.
“Future research efforts should focus on constraining further the extent of melting and runoff from the Greenland ice-sheet and its effects on ocean circulation during the Last Interglacial.”
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Source: UNIVERSITY COLLEGE LONDON
The paper: (open access) https://www.nature.com/articles/s41467-018-06683-3
Enhanced climate instability in the North Atlantic and southern Europe during the Last Interglacial
Abstract
Considerable ambiguity remains over the extent and nature of millennial/centennial-scale climate instability during the Last Interglacial (LIG). Here we analyse marine and terrestrial proxies from a deep-sea sediment sequence on the Portuguese Margin and combine results with an intensively dated Italian speleothem record and climate-model experiments. The strongest expression of climate variability occurred during the transitions into and out of the LIG. Our records also document a series of multi-centennial intra-interglacial arid events in southern Europe, coherent with cold water-mass expansions in the North Atlantic. The spatial and temporal fingerprints of these changes indicate a reorganization of ocean surface circulation, consistent with low-intensity disruptions of the Atlantic meridional overturning circulation (AMOC). The amplitude of this LIG variability is greater than that observed in Holocene records. Episodic Greenland ice melt and runoff as a result of excess warmth may have contributed to AMOC weakening and increased climate instability throughout the LIG.
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From a former post: Warm is stable – Cold is change https://wattsupwiththat.com/2017/08/01/warm-is-stable-cold-is-change/ the following graphic:
Colder periods generally show a higher temperature variability than warm periods.
And from the Abstract of the Tzedakis study above: “The strongest expression of climate variability occurred during the transitions into and out of the LIG”
The authors also could have concluded:
1. Here it is shown that without any human influence the natural variation during the Eemien outpaced Holocene temperature fluctuations
2. Given the strong Little Ice Age cooling (century scale) and comparable strong recent warming (century scale) the Earth possibly/probably started the transition into the next geological stage: the next glacial. As we know, such transitions are characterized by a larger natural variability, exactly what we have seen the last centuries.
Oh!?
And how did they “prove” that correlation?
Answer, they didn’t; it’s all make believe and confirmation bias.
Well, state of the art in climate models is that every climate is wrong. So, this model is state of the art amongst climate models.
It is how they brought confirmation bias into their fantasy and promptly blamed Greenland and the Arctic’s melt on dangerous warming.
But, the Arctic’s temperatures are quite normal every summer, and Greenland is accreting ice, not melting catastrophically.
I wonder why they didn’t mention Antarctica warming?
Likely because the only part of Antarctica warming up, currently, is the human occupied West Antarctic Peninsula.
Just another climate model delusion.
The Younger Dryas put a damper on the Holocene, slowing down our fall from grace.
Way too many assumptions and weak projections being made on very flimsy evidence. It’s far more complicated than they are assuming it to be and their analysis is no more than a wild guess.
Was there greater natural climate variation during the last interglacial, or is it that we just havent seen the full variation in the current one?
Whenever I see the words, ” Computer model says”I turn off. They are just modern day chrystal balls, and can only tell their users just what those same users programme them in what to say.
What did researchers in matters of weather and climate do before computers. Was it a sort of Dar k Ages in research, or did it produce some really good results. ?
MJE
“Last time it happened naturally, therefore this time. It’s being caused by us.”
Fail.
Richard Lindzen is right.
Climate changes BY ITSELF.
From internal dynamics.
Even with NO OUTSIDE FORCING.
Try to get this.
Erratum
How did that full stop get between the “time” and “it’s”? Shouldn’t be there.
This is a good and meticulous palaeoclimate study. This is real climate science.
We can graciously ignore the AGW genuflection.
The true implications of this clear demonstration of natural climate oscillation is there for all to see.
Typical of genuine research discoveries, it raises a question and paradox – which itself has the potential to lead to further deeper insight. The paradox is this: we know that during glacial periods climate is less stable and more variable. The extreme and violent Dansgaard-Oesger oscillations (“micro-interglacials”) – 5-10 degree C up and down fluctuations in a few centuries – happen during glacial, not interglacial periods.
So generally, climate is more stable during interglacials. But this new research points to warmer interglacials having more variability (eg Eemian) than cooler ones (eg Holocene). Curious and counter-intuitive. WUWT?
What in hell is a “Climate model experiment” other than an oxymoron? Surely, it is nothing more than playing around with input parameters in a theoretical model to produce theoretical outcomes based on predetermined formulae and transfer functions. It is certainly not an “experiment” in the scientific sense of a physical experiment to obtain new, real empirical data.
Is how science dies?
Before we all get too excited, this isn’t news. We knew this from the ice cores.
Simply plotting the last 4 glaciations on top of each other shows why this was blindingly obvious, the last interglacial warming period was known to be inhibited by the extreme cooling events of the older and younger Dryas (of unknown cause but the Milankovitch eccentricity believed to be causal was at its lowest variability for this last interglacial warming) ). The Dryas events returned atmospheric temperatures to the lowest glacial levels while the oceans continued to thaw, as shown by the continuous increase in sea level throughout both events. AS a result the maximum warming that prior ice ages had realised was never reached in the last, and “normal ” interglacial service was delayed by 3-4,000 thousand of the normally warmest years, hence sea levels did not reach their highest levels either. Ours is a rather runtish interglacial. Fact. Obs.
You don’t need a Harvard degree to figure out the blindingly bleeding obvious, see graph. (i). However corroboration by another proxy temperature measurement is helpful when disabusing the climate alarmists of their delusional beliefs that humans are having any noticeable effect of the serious planetary scale business of climate change, based on no real date a, proxy or otherwise, just massively biased models that don’t predict reality because of their mostly incorrect pesumptions as to cause and effect. Here’s the evidence, for those with more opinions than facts. Plot your own from Petit et al and the other named series if you doubt them. Enjoy!
(i) Unless you are a second tier climate so called scientist , hard of physics, in search of unachievable credibility for your unprovable pseudo science, and in need of another grant fix to avoid getting a real job.
Brian
It’s a correct observation that our interglacial is “runtish”. And an interesting idea that the aYD is responsible. I agree that this is possible but would approach it from a different angle.
For one thing, like Margaret Thatcher and society, I don’t believe there is such a thing as the YD. What was real was the Bolling-Alerod (BA) – the warming peak that forms the early bound of the YD. The BA was simply the last DO event. There were 19-20 such events during the last glacial interval. During the extreme and violent Dansgaard-Oesger oscillations (“micro-interglacials”) NH temperatures rose then fell by 5-10 degree C in the course of just a few centuries.
The BA was – in my thinking – a DO event that happened just as glacial termination had begun (with Antarctic Ocean warming). Thus the “YD” is simply the interval in time between the last DO / BA event and the subsequent abrupt glacial termination. Thus the BA was not glacial termination that was aborted by the YD. Instead it was a DO event just before glacial inception.
If so, then you still have a fair point – why did the Holocene end up being runtish – with a weak and delayed warm optimum compared to other interglacials like the Eemian? I would agree that the “YD” phenomenon (abortive followed by stable glacial termination) did sabotage the Holocene. But I would guess that it did so by a resonant effect – by introducing a resonance or harmonic toxic to rapid and strong interglacial inception. Thus the cool interglacial. Oddly the coolness of the Holocene might have made it more stable, if the research reported above in this post is to be believed.
Yes sea level did continue to rise during the “YD”. Which tells us that the sea level rise and “YD” were separate oceanographic processes. Sea level rise was associated with slow Antarctic Ocean warming that had begun 20,000 years ago. It was a global event and the larger and more powerful process, not affected much by the YD, which was a NH only phenomenon and likely linked to an excursion of the AMOC / Gulf Stream.